In measuring the blood pressure of individuals, an air inflatable cuff or band in almost all cases is applied about the upper arm in a region overlying the brachial artery. During the blood pressure measurement, the sleeve is inflated to a pressure lying above systolic pressure and then slowly vented. In that case, Korotkoff tapping sounds are detected with the device such as a stethoscope applied to the brachial artery below the blood occluding portion of the cuff. As is well known, detection of the first Korotkoff sounds and then detection of the sounds becoming muffled or ceasing indicate, respectively, the systolic and diastolic blood pressure of the patient.
At the present time a standard cuff or band having a width of about 12 centimeters is used in almost all instances irrespective of the build or size of the patient. It is well known at the present time that because of the existence of soft tissue between the blood vessel and the bone in the limb (arm or thigh) the real blood pressure measured with the same cuff is ambiguous for different arm thicknesses despite the same pressure being indicated on the manometer. In fact, tests have indicated that errors in the order of 5-10 mm. Hg., and sometimes considerably greater, may exist as to both the systolic and diastolic pressures. Such an error may in some instances be quite decisive as to whether a patient is considered sick or not sick and is to be treated or not treated.
To overcome this error it has been determined that the width of the distensible part of the bladder overlying the artery should be approximately 40% of the circumference of the limb to properly occlude the artery. The American Heart Association (AHA) has recommended a total of seven different cuff sizes to cover a range of arm widths from pediatric to large adult with a plus or minus 5% error. In carrying out the recommendations the individual taking the blood pressure measurement would first have to measure the arm of the patient and then choose the appropriate cuff. It is widely known that such a procedure is not used in a vast majority of wards or clinics or physicians offices. The standard 12 centimeter cuff is instead used in virtually all blood pressure measurements with the attendant inaccuracies.
To solve this problem, blood pressure measuring equipment has been provided to automatically compensate for the varying arm sizes through the medium of providing cuffs with portions thereof which may be selectively inflated while throttling other portions to thus accommodate varying sized arms of patients. Such structures are shown in U.S. Pat. Nos. 3,812,844, 3,906,937, and 4,572,205.
An additional problem attendant measurement of blood pressure exists where the extensible bladder of the cuff or band passes around the arm of the patient. It is recognized that if the distensible bladder extends around the patients arm circumference only once, the likelihood of a more accurate measurement is enhanced. Solutions to this problem by way of inflating only that portion of the bladder which surrounds the patients arm a single time is shown in U.S. Pat. Nos. 1,288,130 and 1,857,567 each of which enables inflation of only a portion of the bladder.
In addition to the foregoing, U.S. Pat. No. 4,501,280 discloses an automated system including appropriate sensors and a microprocessor for automatically measuring the blood pressure while using different size cuffs ranging from conventional to neonatal depending upon patient size.